CT Attenuation of Acute Subdural Hematomas in Patients with Anemia.

BACKGROUND AND PURPOSE: Isodense and hypodense acute subdural hematomas have been reported in the literature in anemic patients. The purpose of this study is to see if there is a statistically significant difference between the Hounsfield unit measurements of acute subdural hematomas in anemic and nonanemic patients. METHODS: A total of 109 patients were analyzed. We measured the most hyperdense component of the subdural hematoma and compared these measurements for both anemic and nonanemic patients. RESULTS: All patients with anemia had a hyperdense component to their subdural hematomas during the acute period. No statistically significant difference was found in the density of the subdural hematomas between the two groups. More heterogeneous subdural hematomas were found in the anemic group than the nonanemic group, which suggests that anemia alone is not a sufficient explanation for acute homogenous isodense and hypodense subdural hematomas. CONCLUSION: A hyperdense subdural component was present in all acute subdural hematomas in anemic patients. Therefore, anemia alone is not a sufficient explanation for a homogenous low-density acute subdural hematoma.

Does CT-based Rigidity Analysis Influence Clinical Decision-making in Simulations of Metastatic Bone Disease?

BACKGROUND: There is a need to improve the prediction of fracture risk for patients with metastatic bone disease. CT-based rigidity analysis (CTRA) is a sensitive and specific method, yet its influence on clinical decision-making has never been quantified. QUESTIONS/PURPOSES: What is the influence of CTRA on providers' perceived risk of fracture? (2) What is the influence of CTRA on providers' treatment recommendations in simulated clinical scenarios of metastatic bone disease of the femur? (3) Does CTRA improve interobserver agreement regarding treatment recommendations? METHODS: We conducted a survey among 80 academic physicians (orthopaedic oncologists, musculoskeletal radiologists, and radiation oncologists) using simulated vignettes of femoral lesions presented as three separate scenarios: (1) no CTRA input (baseline); (2) CTRA input suggesting increased risk of fracture (CTRA+); and (3) CTRA input suggesting decreased risk of fracture (CTRA-). Participants were asked to rate the patient's risk of fracture on a scale of 0% to 100% and to provide a treatment recommendation. Overall response rate was 62.5% (50 of 80). RESULTS: When CTRA suggested an increased risk of fracture, physicians perceived the fracture risk to be slightly greater (37% ± 3% versus 42% ± 3%, p < 0.001; mean difference [95% confidence interval {CI}] = 5% [4.7%-5.2%]) and were more prone to recommend surgical stabilization (46% ± 9% versus 54% ± 9%, p < 0.001; mean difference [95% CI] = 9% [7.9-10.1]). When CTRA suggested a decreased risk of fracture, physicians perceived the risk to be slightly decreased (37% ± 25% versus 35% ± 25%, p = 0.04; mean difference [95% CI] = 2% [2.74%-2.26%]) and were less prone to recommend surgical stabilization (46% ± 9% versus 42% ± 9%, p < 0.03; mean difference [95% CI] = 4% [3.9-5.1]). The effect size of the influence of CTRA on physicians' perception of fracture risk and treatment planning varied with lesion severity and specialty of the responders. CTRA did not increase interobserver agreement regarding treatment recommendations when compared with the baseline scenario (κ = 0.41 versus κ = 0.43, respectively). CONCLUSIONS: Based on this survey study, CTRA had a small influence on perceived fracture risk and treatment recommendations and did not increase interobserver agreement. Further work is required to properly introduce this technique to physicians involved in the care of patients with metastatic lesions. Given the number of preclinical and clinical studies outlining the efficacy of this technique, better education through presentations at seminars/webinars and symposia will be the first step. This should be followed by clinical trials to establish CTRA-based clinical guidelines based on evidence-based medicine. Increased exposure of clinicians to CTRA, including its underlying methodology to study bone structural characteristics, may establish CTRA as a uniform guideline to assess fracture risk. LEVEL OF EVIDENCE: Level III, economic and decision analyses.

Correlation of the Strength of Recommendations for Additional Imaging to Adherence Rate and Diagnostic Yield.

PURPOSE: The aim of this study was to evaluate the association between the wording of radiologist recommendations for chest CT with the likelihood of recommendation adherence and the diagnostic yield of the recommended follow-up CT imaging. METHODS: This HIPAA-compliant retrospective study had institutional review board approval, including waiver of the requirement for patient consent. All outpatient chest radiographic (CXR) studies performed at a tertiary care academic medical center in 2008 (n = 29,138) were searched to identify examinations with recommendations for chest CT. The wording of chest CT recommendations was classified as conditional or absolute, on the basis of whether the recommendation stood independent of the clinical judgment of the ordering clinician. Using the radiology information system, patients who underwent chest CT within 90 days of the index CXR study containing the recommendation were determined, and the CT studies were evaluated to determine if there were abnormalities corresponding to the CXR abnormalities that prompted the recommendations. Corresponding abnormalities were categorized as clinically relevant or not, on the basis of whether further workup or treatment was warranted. Groups were compared using t tests and Fisher exact tests. RESULTS: Recommendations for chest CT appeared in 4.5% of outpatient CXR studies (1,316 of 29,138; 95% confidence interval [CI], 4.3%-4.8%); 39.4% (519 of 1,316; 95% CI, 36.8%-42.0%) were conditional and 60.6% (797 of 1,316; 95% CI, 58.0%-63.2%) were absolute. Patients with absolute recommendations were significantly more likely to undergo follow-up chest CT within 90 days than patients with conditional recommendations (67.8% vs 45.8%, respectively, P < .001). Despite this difference in provider adherence, there was no significant difference between the conditional and absolute recommendation groups with regard to the incidence of clinically relevant corresponding findings (P = .16) or malignancy (P = .08) on follow-up CT. CONCLUSIONS: Conditional radiologist recommendations are associated with decreased provider adherence, though the likelihood of a clinically relevant finding on follow-up CT is no different than with absolute recommendations.

Improving education for the management of contrast reactions: an online didactic model.

PURPOSE: Radiologists could improve their knowledge of contrast reaction management. The aim of this study was to evaluate to what degree the implementation of a didactic module resulted in improved technologist, nurse, and physician knowledge and comfort levels regarding the appropriate management of adverse reactions to contrast media. METHODS: After institutional review board approval was obtained, nurses, technologists, and physicians involved in contrast administration were required to complete the educational module. Premodule and postmodule assessments were designed online. Each assessment included knowledge-based questions regarding the appropriate management of different types of contrast reactions, as well as questions regarding each respondent's comfort level with the treatment of various types of adverse contrast reactions. Comfort level was measured using a 6-point, Likert-type scale. Premodule and postmodule assessment scores were compared using McNemar's test. RESULTS: After module completion, physicians demonstrated a statistically significant improvement in knowledge regarding the proper administration route, concentration, and dose of intramuscular epinephrine. Physicians demonstrated significantly increased comfort with the administration of intramuscular epinephrine to adult and pediatric patients after module completion (P < .05). Module completion resulted in statistically significant improvements in respondents' comfort levels with the treatment of an adverse reaction to contrast media, although 19% of personnel still reported feeling uncomfortable after completing the module. CONCLUSIONS: Didactic instruction in contrast reaction management results in improved knowledge and comfort levels for physicians, nurses, and technologists. However, a significant percentage of personnel still reported feeling uncomfortable treating an adverse contrast reaction after module completion, suggesting that didactic instruction alone may be inadequate.

Further improvements on the factors affecting bone mineral density measured by quantitative micro-computed tomography.

The effects of imaging parameters and special configuration of objects within the reconstruction space on the micro computed tomography (µCT) based mineral density have been explored, and a series of density correction curves have been presented. A manufacturer-provided calibration phantom (0, 100, 200, 400, 800 mg HA/cm(3)) was imaged at all possible imaging conditions (n=216) based on energy, resolution, vial diameter, beam hardening correction factor and averaging. For each imaging condition, a linear regression model was fitted to the observed versus expected densities, and the intercepts (ß(0)) and slopes (ß(1)) of the regression lines and each density level were modeled using multiple regression modeling. Additionally, a custom made phantom (0, 50, 150, 500, 800, 1000 and 1500 mg HA/cm(3)) was scanned in order to study the effects of location and orientation of an object within the reconstruction space and presence of surrounding objects on µCT based mineral density. The energy, vial diameter and beam hardening correction factor were significant predictors of cumineral density (P values<0.001), while averaging and resolution did not have a significant effect on the observed density values (P values>0.1) except for 0.0 density (P values<0.04). Varying the location of an object within the reconstruction space from the center to the periphery resulted in a drop in observed mineral density up to 10% (P values<0.005). The presence of surrounding densities resulted in decreased observed mineral density up to 17% at the center and up to 14% at the periphery of the reconstruction space (P values<0.001 for all densities). Changing the orientation of the sample also had a significant effect on the observed mineral density, resulting in up to 16% lower observed mineral density for vertical vs. horizontal orientation at the center of the reconstruction space (P value<0.001). We conclude that energy, resolution and post processing correction factor are significant predictors of the observed mineral density in µCT.

Non-invasive assessment of failure torque in rat bones with simulated lytic lesions using computed tomography based structural rigidity analysis.

This study applies CT-based structural rigidity analysis (CTRA) to assess failure torque of rat femurs with simulated lytic defects at different locations (proximal and distal femur) and diameters (25% and 50% of the cross-section at the site), and compared the results to those obtained from mechanical testing. Moreover, it aims to compare the correlation coefficients between CTRA-based failure torque and DXA-based aBMD versus actual failure torque. Twenty rats were randomly assigned to four equal groups of different simulated lesions based on size and location. Femurs from each animal underwent micro-computed tomography to assess three-dimensional micro-structural data, torsional rigidity using structural rigidity analysis and dual energy X-ray absorptiometry to assess bone mineral density. Following imaging, all specimens were subjected to torsion. Failure torque predicted from CT-derived structural rigidity measurements was better correlated with mechanically derived failure torque [R(2)=0.85] than was aBMD from DXA [R(2)=0.32]. In summary, the results of this study suggest that computed tomography based structural rigidity analysis can be used to accurately and quantitatively measure the mechanical failure torque of bones with osteolytic lesions in an experimental rat model. Structural rigidity analysis can provide more accurate predictions on maximal torque to mechanical failure than dual energy X-ray absorptiometry based on bone mineral density.

Increasing the appropriateness of outpatient imaging: effects of a barrier to ordering low-yield examinations.

PURPOSE: To determine the effect of a computerized radiology order entry system rule that prevented nonclinician support staff from completing orders for outpatient computed tomographic, magnetic resonance imaging, and nuclear medicine examinations that received initial low-yield decision support scores in the order entry system. MATERIALS AND METHODS: This retrospective HIPAA-compliant study was approved by the institutional review board; the requirement for informed consent was waived. The control group consisted of 42737 consecutive orders for examinations in which decision support was provided that were placed from April to December 2006. The study group consisted of 76238 consecutive orders that were placed from April to December 2007. During the latter time period, a new rule in the order entry system was implemented: Examinations that had low-yield decision support scores could not be scheduled when the orders were placed by nonclinician support staff. To schedule the blocked examinations, the responsible clinician was required to personally log in to complete the process. System event logs and records of outpatient imaging procedures were extracted, counted, and analyzed to determine which ordering sessions resulted in examinations being scheduled and performed and which sessions resulted in modified or cancelled examinations. Results were correlated with user status and decision support scores. The Cochran-Mantel-Haenszel technique was used to control for the status of the order initiator and to allow testing for significance of the effect of the intervention on the "fate" of ordering events. RESULTS: After the intervention, the proportion of total examination requests initiated by clinicians directly logging in almost doubled: from 11,243 (26.31%) of 4,737 to 41,450 (54.37%) of 76238 examinations (P < .001). The fraction of low-yield (decision support score, 1-3) examinations requested through the order entry system that were later scheduled and performed decreased from 2106 (5.43%) of 38,801 to 1261 (1.92%) of 65,765 (P < .001). This is in contrast to requests for examinations with higher initial decision support scores that were not affected by the policy change and were scheduled at the same rate (relative risk, 0.988) before and after the change. CONCLUSION: A simple change in the business logic of the order entry system resulted in a substantially decreased rate of low-yield imaging examinations and a markedly increased percentage of tests personally ordered by clinicians.

Compressive axial mechanical properties of rat bone as functions of bone volume fraction, apparent density and micro-ct based mineral density.

Mechanical testing has been regarded as the gold standard to investigate the effects of pathologies on the structure-function properties of the skeleton. With recent advances in computing power of personal computers, virtual alternatives to mechanical testing are gaining acceptance and use. We have previously introduced such a technique called structural rigidity analysis to assess mechanical strength of skeletal tissue with defects. The application of this technique is predicated upon the use of relationships defining the strength of bone as a function of its density for a given loading mode. We are to apply this technique in rat models to assess their compressive skeletal response subjected to a host of biological and pharmaceutical stimulations. Therefore, the aim of this study is to derive a relationship expressing axial compressive mechanical properties of rat cortical and cancellous bone as a function of equivalent bone mineral density, bone volume fraction or apparent density over a range of normal and pathologic bones. We used bones from normal, ovariectomized and partially nephrectomized animals. All specimens underwent micro-computed tomographic imaging to assess bone morphometric and densitometric indices and uniaxial compression to failure. We obtained univariate relationships describing 71-78% of the mechanical properties of rat cortical and cancellous bone based on equivalent mineral density, bone volume fraction or apparent density over a wide range of density and common skeletal pathologies. The relationships reported in this study can be used in the structural rigidity analysis introduced by the authors to provide a non-invasive method to assess the compressive strength of bones affected by pathology and/or treatment options.

An improved method to assess torsional properties of rodent long bones.

Torsion is an important testing modality commonly used to calculate structural properties of long bones. However, the effects of size and geometry must be excluded from the overall structural response in order to compare material properties of bones of different size, age and species. We have developed a new method to analyze torsional properties of bones using actual cross-sectional information and length-wise geometrical variations obtained by micro-computed topographic (microCT) imaging. The proposed method was first validated by manufacturing three rat femurs through rapid prototyping using a plastic with known material properties. The observed variations in calculated torsional shear modulus of the hollow elliptical model of mid-shaft cross-section (Ekeland et al.), multi-prismatic model of five true cross-sections (Levenston et al.) and multi-slice model presented in this study were 96%, -7% and 6% from the actual properties of the plastic, respectively. Subsequently, we used this method to derive relationships expressing torsional properties of rat cortical bone as a function of muCT-based bone volume fraction or apparent density over a range of normal and pathologic bone densities. Results indicate that a regression model of shear modulus or shear strength and bone volume fraction or apparent density described at least 81% of the variation in torsional properties of normal and pathologic bones. Coupled with the structural rigidity analysis technique introduced by the authors, the relationships reported here can provide a non-invasive tool to assess fracture risk in bones affected by pathologies and/or treatment options.